PbS quantum dots-induced trap-assisted charge injection in perovskite photodetectors

Abstract

In this study, we report solution-processed photodetectors fabricated by methylammonium triiodide perovskite (CH 3 NH 3 PbI 3) incorporated with PbS quantum dots (QDs) through the trapassisted charge-injection effect. In order to increase the photo-responsivity by eliminating the charge injection barrier from the cathode electrode, PbS QDs, which possesses large amount of trap states, are introduced into the CH 3 NH 3 PbI 3 thin film for establishing ohmic contact at the CH 3 NH 3 PbI 3 /aluminum (Al) interface. As a result, an external quantum efficiency of ~4500 %, a photoresponsivity of ~15000 mA/W and a detectivity of over 6×10 13 Jones (1 Jones=1 cmHz 1/2 W-1) at a small bias of 2 volts, and a photoresponse time of 11.5 µs are observed from the solution-processed photodetectors fabricated by the CH 3 NH 3 PbI 3 :PbS QDs nanocomposites thin film.

Solution‐Processed Flexible Broadband Photodetectors with Solution‐Processed Transparent Polymeric Electrode

“…The second functionality of the CH 3 NH 3 PbI 3 /PbSe QDs bilayer thin film is to boost responsivity ( R ) and projected detectivity ( D *) of broadband PDs in both visible and IR regions through the trap‐assisted photomultiplication (PM) effect. [ 5f,28 ] Figure 2c displays the lowest unoccupied molecular orbital (LUMO) and the HOMO energy levels of PTAA, CH 3 NH 3 PbI 3 , PbSe QDs, C 60 , and the work‐functions of FAI‐treated PEDOT:PSS and Al electrodes. The HOMO energy level of the FAI‐treated PEDOT:PSS thin film is estimated to be −4.80 eV by cyclic voltammetry (CV) method from oxidation and reduction potentials (Figure S4, Supporting Information 1).…”

“…However, under illumination, excitons generated in the CH 3 NH 3 PbI 3 /PbSe QDs photoactive layer would dissociate into separated charge carriers under a small external electric field. [ 5f,28 ] The separated holes would be transported from CH 3 NH 3 PbI 3 layer to the FAI‐treated PEDOT:PSS anode through the PTAA HEL. The separated electrons would be transferred from CH 3 NH 3 PbI 3 into PbSe QDs due to the small LUMOs offset between CH 3 NH 3 PbI 3 and PbSe QDs.…”

Recent Progress on Photomultiplication Type Organic Photodetectors

“…Gong et al. successfully fabricated highly sensitive solution‐processed PPDs with PM by the incorporation of PbS QDs into MAPbI 3 active layer, utilizing trap‐assisted charge tunneling injection effect . The trap states formed by PbS QDs near the surface of the MAPbI 3 thin film could down‐shift the LUMO energy level of the MAPbI 3 thin film and adjust the energy level alignment at the MAPbI 3 /Al cathode interface, thus forming the ohmic contact for effective hole injection from the Al cathode.…”

“…The hole traps caused by large concentration of Pb 2+ cations in perovskite film top surface is critical for realizing high PM in these devices. In addition to the working mechanism of PM type PPDs based on charge tunneling injection induced by interfacial traps, there are two possible mechanisms to realize photocurrent multiplication in PPDs with vertical structure: i) interface‐barrier‐modification mechanism via field‐driven ion migration, and ii) ferroelectric polarization mechanism …”

Low‐Bandgap Terpolymers for High‐Gain Photodiodes with High Detectivity and Responsivity from 300 nm to 1600 nm

“…The steady‐state photocurrent under 800‐nm light illumination with variable powers from 9.47 nW/cm 2 up to 0.11 W/cm 2 under 2.0 V were recorded for the P2‐based photodiode. A linear correlation between the photocurrent and light intensity from 9.47 nW/cm 2 to 2.95 mW/cm 2 was obtained, which corresponds to a large LDR of 100 dB (Figure S12) ,…”